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Signs of a Bad EGR Valve: Your Ultimate Guide!


The EGR or exhaust gas recirculation valve is a vital component of the engine management system of a car. It is responsible for recirculating precisely metered amounts of exhaust gas to the engine intake system. This can lead to an increased engine performance, increased fuel economy, and reduced NOx emissions. Over time, the EGR valves suffer wear and tear or damage due to carbon particles building up from the exhaust gasses along the EGR and intake system passages. When this happens, you will experience signs of a bad EGR valve that include rough idling, fuel smell, poor engine performance, knocking sounds, increased emissions, poor fuel economy, failed smog test, and an illuminating check engine light.

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Signs of a Bad EGR Valve: How Will You Know if You Have a Bad EGR Valve?



Before we discuss the signs of a bad EGR valve and how it can affect your car, we need to understand what an EGR valve is and how it works. EGR stands for exhaust gas recirculation, which is used in both gasoline and diesel engines for vehicle emissions control. It is a method used to manage nitrogen oxides emissions which is a byproduct during the combustion process. The EGR valve is a main component of a car’s engine health and exhaust system. Depending on the age of the car or whether it is powered by gasoline or diesel fuel, the EGR valve may work differently.


The combustion process requires air, which is usually a combination of Oxygen and Nitrogen, and it will be mixed with fuel which will then ignite in the combustion chamber. This will cause the temperatures to increase that will lead to the creation of NOx emissions, which is known to be harmful to the environment.


This is why the EGR system is vital, it works by returning small amounts of exhaust gas to the combustion chamber through the intake manifold. This lowers the combustion temperatures which helps lessen the NOx amount emitted into the atmosphere. The EGR valve which is usually closed, plays a big role in this EGR system.


The valve links together the exhaust manifold and the intake manifold. It is managed or controlled by either a built-in electric step motor or a vacuum. The task of an EGR valve is basically to control the exhaust gas flow being recirculated by the system depending on the engine load. It will start to work when the engine has turned, achieved its normal operating temperature, and when the speed of the car rises. The EGR valve will then gradually control the flow of exhaust gasses. When the car decelerates or the engine stops, the EGR valve will then return to its closed position to keep the exhaust gasses from flowing.


The EGR valve is prone to damage over time due to wear and tear since it is always exposed to extreme temperatures. The most common reason why an EGR valve fails is carbon deposit build ups. This can result in clogged EGR passages or tubes that can prevent the process of recirculating the exhaust gasses. A bad EGR valve can also be due to a leak or rupture in the valve diaphragm.


So you ask, how will you know if you have a bad EGR valve? If your EGR valve is failing , you will experience signs of a bad EGR valve, which includes:



  • Poor fuel economy


The EGR valve works by providing the correct amount of exhaust back to the combustion chamber. This can result in a reduced temperature of the combustion chamber and improves its efficiency. But when a faulty EGR valve is stuck in an open position, it can lead to the engine sucking in air that is already measured by the mass air flow sensor, leading to a lean air and fuel mixture. When this happens, a significant drop of your car’s fuel economy will be noticed.


This problem can happen since the combustion chambers’ temperature inside tends to be lower, which leads to the fuel inside to not ignite as quickly as it’s supposed to. When you experience this problem, you need to correct it immediately to prevent any further damage.


  • Rough Idling


Rough idling is one of the signs of a bad EGR valve and it can happen when your EGR valve is stuck in an open position. This problem lets too much exhaust gas into your combustion chamber since it is always open, allowing constant flow of exhaust gas into the intake manifold.  When this happens, it can throw off the air and fuel mixture inside it. This causes your engine to idle roughly.


  • Increased emissions


One of the signs of a bad EGR valve is increased emissions and this can happen since the main task of an EGR valve is to reduce emissions. When it is faulty, it won’t be able to do its job properly. You might fail your car’s emissions test when this happens. You might be able to see that the amount of smoke in your exhaust has increased, but sometimes you won’t be able to.


Increased emissions should be fixed immediately since it means that an increased flow of unburned hydrocarbon gasses will be emitted out of your car and into the atmosphere, which will most likely happen when your bad EGR valve is stuck in an open position.  When your valve is stuck in a closed position, the high temperature in the combustion chamber can allow an excessive formation of harmful NOx gasses, which is also very harmful to the environment.


  • Illuminating check engine light


The car’s onboard computer will let you know and alert you that something is wrong within the system by triggering your check engine light to illuminate. This can happen when the sensors in your car, which are many, have detected that your EGR valve is clogged, stuck closed, or open. But since a check engine light can also be triggered by some other problem, it is better to have your car checked when you notice that your check engine light is on to determine what really caused it and have it corrected.



  • Poor engine performance


Poor engine performance is also one of the signs of a bad EGR valve and is probably the first symptom you’ll ever encounter or notice. Bear in mind that the EGR system helps enhance the fuel economy as well as improve the engine’s performance. If the EGR valve is failing, you might notice that the engine’s efficiency and performance has decreased. You may usually be able to detect this problem at lower speeds when the EGR valve is stuck in an open position and at higher speeds when the valve is stuck closed.


  • Fuel smell


If your EGR valve is already failing, your car’s engine will take up more fuel than usual and this can result in more hydrocarbons being emitted from your car’s tailpipe. When this happens, it can lead to an increased amount of fuel fumes and you will be able to smell it inside your car cabin, mostly at times when your car’s air conditioning is not in recirculation mode.


This should not happen because the EGR valve is there, equipped in your car, to help get rid or lessen the amount of NOx emissions from your tailpipe. If you notice a fuel smell inside your car, have it checked immediately and have the problem corrected.


  • Knocking noises


One of the advantages of having a healthy EGR valve equipped in your car is that it can lessen engine knocking. This can be achieved when the combustion is kept at a lower temperature, since it can prevent the fuel from igniting before it’s supposed to.


If you notice knocking noises from your engine, it can be because of a bad EGR valve stuck closed. The temperature inside the combustion chambers will increase and when the car is at low rpm when this happens. The fuel may ignite early when it meets the high temperature and this is what causes the knocking sound, when the bad EGR valve is stuck closed.



Signs of a Bad EGR Valve: How Do You Test an EGR Valve?



If you experience any of the signs of a bad EGR valve, you will want to make sure whether the problems are really caused by a bad EGR valve or by something else. To determine if they are really signs of a bad EGR valve, you can test your EGR valve.


To test an EGR valve, you just need to follow the following procedures:


  • Turn on your car’s engine and let it run until it reaches its normal operating temperature.
  • Open the hood of your car and latch it in place.
  • Find the vacuum line at the EGR valve and disconnect it.
  • Then attach a hand vacuum pump to your EGR valve.
  • Apply the vacuum continuously until the EGR valve opens. When the EGR valve opens, the engine may start to idle and it might even stall. If this happens whenever the valve is opened and stops when you pull away the vacuum from the valve, then it means that the EGR partitions are working fine and are not leaking, the exhaust pipes from the exhaust traverse located on the intake manifold are working fine and allow exhaust gas recirculation, and that the valve are seated tightly when it is closed.
  • You will know if you have a bad EGR valve that warrants a replacement when it fails to open when you apply the vacuum pump to it.


You can also test your EGR valve by using a vacuum gauge. To do this method, you will have to follow these steps.


  • Do this method with a cold engine. Do not try to warm it.
  • Find the vacuum line at the EGR valve and unplug it. Then equip a tee and vacuum gauge.
  • Reconnect the vacuum line to the EGR valve.
  • Turn your key in the ignition and turn on your engine. Check the gauge. It should read zero.
  • Step on the gas pedal and accelerate the engine until it reaches 2,000 RPM. Check the gauge and it should still read zero.
  • Let the engine run until it warms up to its normal operating temperature.
  • Step on the gas pedal again and accelerate the engine until it reaches 2,000 RPM. Check the gauge again and this time, it should have a reading of between 1 and 4.
  • At this point, if you get a zero reading, it means that the CTO switch is not working as it should.


If you ask, will a bad EGR valve throw a code? Yes, it will. A faulty EGR valve will throw any of the following codes:


  • P0400 – EGR flow malfunction
  • P0401 – EGR insufficient flow detected
  • P0402 – EGR excessive flow detected
  • P0403 – EGR circuit malfunction
  • P0404 – EGR circuit range or performance
  • P0405 – EGR sensor A circuit low
  • P0406 – EGR sensor A circuit high
  • P0407 – EGR sensor B circuit low
  • P0408 – EGR sensor B circuit high
  • P1403 – EGR solenoid low
  • P1404 – EGR system – closed valve pintle error
  • P1405 – EGR solenoid high
  • P1406 – EGR system pintle position error



How Much Does it Cost to Replace an EGR Valve?



If you are experiencing the signs of a bad EGR valve, you might want to know how much it will cost to replace it. An EGR valve replacement can cost around $150 to $700, including parts and labor. The total cost can vary depending on your car’s make and model as well as the shop you choose to do the replacement. However, a faulty EGR valve that is only clogged or stuck open or closed because of some build ups or soot particles can be repaired by just cleaning it up. You can clean the EGR valve yourself if you know your way around cars.


When you experience any of the signs of a bad EGR valve, it is important that you address the problem immediately. Not only does a faulty EGR valve reduce the performance and efficiency of your car, it can also cause harmful gasses to be released in the environment.

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